1. Field of the Invention
This invention relates to the hydrocyanation of unsaturated nitriles, e.g., 3- and 4-pentenenitriles using a zerovalent nickel catalyst promoted by triorganotin compounds.
2. Description of Related Art
U.S. Pat. No. 2,571,099, issued on Oct. 16, 1951 to Paul Arthur, Jr. et al. discloses the use of nickel carbonyl with or without the addition of a tertiary aryl phosphine or arsine. This process produces a relatively high percentage of undesirable polymeric products when applied to nonconjugated olefinic starting materials and a relatively poor yield in all cases.
U.S. Pat. No. 3,496,217 issued on Feb. 17, 1970 to W. C. Drinkard et al. discloses an improvement in hydrocyanation using a large number of metal cation compounds with a variety of anions as catalyst promoters. More particularly, the patent discloses as a promoter a cation of zinc, cadmium, beryllium, aluminum, gallium, indium, silver, titanium, zirconium, hafnium, germanium, tin, vanadium, niobium, scandium, chromium, molybdenum, tungsten, manganese, rhenium, palladium, thorium, erbium, iron and cobalt, or mixtures thereof. Preferred anions are halide, i.e., fluoride, chloride, bromide, and iodide; anions of lower fatty acids of from 2 to 7 carbon atoms, HPO.sub.3.sup.-2, H.sub.2 PO.sub.2.sup.-, CF.sub.3 COO.sup.-, OSO.sub.2 C.sub.7 F.sub.15.sup.- and SO.sub.4.sup.-, etc. The known organometallic compounds (C.sub.2 H.sub.5).sub.3 Al.sub.2 Cl.sub.3, and C.sub.2 H.sub.5 AlCl.sub.2 are also disclosed as promoters.
U.S. Pat. No. 3,496,218 issued on Feb. 17, 1970 to W. C. Drinkard discloses a nickel hydrocyanation catalyst promoted with various boron-containing compounds, including triphenylboron and alkali metal borohydrides.
U.S. Pat. No. 3,925,445 issued on Dec. 9, 1975 to C. M. King et al. discloses zerovalent nickel hydrocyanation catalysts promoted with metal halides and organoboron compounds.
U.S. Pat. No. 3,852,325 issued on Dec. 3, 1974 to C. M. King teaches that along with production of 3-pentenenitrile (3PN) in the hydrocyanation of butadiene there is also obtained varying amounts of cis- and trans-2-pentenenitriles (C-2PN and T-2PN) and that these 2-pentenenitriles are found to be detrimental to catalyst efficiency in the hydrocyanation of 3PN or 4-pentenenitrile (4PN) to adiponitrile (ADN). The patentee also teaches that T-2PN cannot be removed satisfactorily from a mixture of pentenenitriles by fractional distillation, for example, because its boiling point is too close to that of other pentenenitriles such as 3PN or 4PN. Isomerizing T-2PN to the more volatile C-2PN which in turn can be removed from the reaction mixture by fractional distillation is discussed.
A recent description of a hydrocyanation process can be found in U.S. Pat. No. 4,082,811 issued on Apr. 4, 1978.
A general discussion of triorganotin compounds and their use a catalysts for the Diels-Alder addition is found in an article by W. A. Nugent et al. appearing in Organometallics, Vol. 3, No. 8, pp. 1315-17 (1985). The function of the Lewis acid .phi..sub.3 SnO.sub.2 CCF.sub.3 as a catalyst for the isomerization but not hydrocyanation of 3PN is discussed in the article by C. A. Tolman et al. entitled "Homogenous Nickel Catalyzed Olefin Hydrocyanation", Advances in Catalysts, 33, pp. 1-46 (1985).